In the production process of printed wiring boards, commonly a plating resist or an etching resist is formed on the copper layer surface using a photosensitive resin (photoresist), and patterning is performed. For example, in a semi-additive process, a copper layer called a “seed layer” is formed on an insulated board by electroless plating, a plating resist is formed on the seed layer, and then pattern plating is performed by copper electroplating to form patterned metal wiring at a resist opening on the seed layer.
As a pretreatment for forming a resin layer such as a resist on a copper layer such as a seed layer, the copper layer surface is roughened. The roughening treatment is intended not only to activate the copper layer surface but also to improve adhesion to a resist with an anchoring effect by roughening the copper layer surface.
As a method for roughening, conventionally known is a method of roughening the copper layer surface with a microetching solution containing a specific polymer compound as described in Patent Document 1 or a microetching solution containing a specific organic acid as described in Patent Document 2. According to the above mentioned roughening method, adhesion between the copper layer surface and a resist can be improved because deep irregularities are formed on the copper layer surface.